Study of an error-prone hypercycle formed from two kinetically distinguishable species.

Asymmetry within both the amplification factor values (Ak) and cross-catalytic hypercyclic constant (Kjk) and its influence on the stability of a two-membered error-prone hypercycle has been exhaustively studied from a deterministic point of view and the bifurcation diagram as a function of the quality factor (Q) has been obtained. In the more general case, several Q critical values appear, changing their relative position in the diagram depending on the Ak and Kjk values. The order of the Q critical values affects both the general properties of the system and the stability of the hypercyclic organization. The importance of this asymmetry in the selective and evolutionary properties of the hypercycle is also discussed.

Transition state of the glycolytic pathway under FDP saturating conditions: experimental studies and a theoretical model.

1. The transition state of the glycolytic pathway, under FDP saturating conditions, from no ADP to ADP-saturating levels, is studied in a metabolic model in vitro obtained from rat skeletal muscle. 2. When ADP is absent from the reaction mixture a steady state for NADH concentration is observed. After ADP addition, a new steady state is reached. The transition state from the first steady state to the second one shows a pulse of NADH. Both the profile and the size of this pulse depend on the enzyme concentration. 3. A kinetic model of the lower part of glycolysis (after PFK reaction) is proposed, and this is described by a set of first order coupled nonlinear differential equations. The results obtained through stability analysis and numerical integration of these equations agree with the experimental ones. 4. The possible role of the above mentioned transition state on the transmitter mechanism of glycolytic oscillations from PFK to the lower part of the glycolysis is discussed.